Integrated Fiber Bragg Grating accelerometer in a surgical instrument

ABSTRACT

An accelerometer is included within the confined space and limited volume of a distal portion of a surgical instrument. The surgical instrument includes an end component, a joint coupled to the end component, a shaft coupled to the joint, and a force transducer and accelerometer apparatus. The force transducer and accelerometer apparatus is coupled between the joint and the shaft. The force transducer and accelerometer apparatus includes a force sensor and an accelerometer. The accelerometer includes an optic fiber having a Fiber Bragg Grating. Information acquired from the Fiber Bragg Grating is used to drive a vibro-tactile haptic feedback output device coupled to a master control arm surgeon grip.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/727,241 (filed 6 Oct. 2017), which is a continuation of U.S. patentapplication Ser. No. 14/540,313 (filed 13 Nov. 2014), which claimspriority to and the benefit of U.S. Patent Application No. 61/903,874(filed 13 Nov. 2013), the full disclosures of each which areincorporated herein by reference for all purposes.

BACKGROUND Field of Invention

Aspects of this invention are related to surgical instruments, and aremore particularly related to an accelerometer mounted on a surgicalinstrument.

Related Art

Accelerometers are widely used to measure shocks and vibrations. Fiberoptic accelerometers are known and are in commercial use. In particular,fiber optic accelerometers that utilize Fiber Bragg Grating have beendeveloped. Generally, prior Fiber Bragg Grating (FBG) accelerometers areof three types—axial FBG accelerometers, flexural FBG accelerometers,and hybrids of axial and flexural accelerometers.

FIG. 1A illustrates a first example of an axial FBG accelerometer 100. Apre-tensioned optic fiber 102 includes two FBGs 102A, 102B. A mass 101is affixed to optic fiber 102 and positioned between FBGs 102A and 102B.The inertial reaction of mass 101 to a shock causes FBGs 102A and 102Bto stretch or un-stretch in response to accelerations of the mass alongthe direction of optic fiber 102. FBGs 102A, 102B are located along themeasurement axis of accelerometer 100, and are read differentially toprovide temperature compensation.

An axial FBG accelerometer can have accelerometers positioned on one,two, or three axes. For example, FIG. 1B shows a tri-axial accelerometer110. A mass 111 is positioned between FBGs 112A and 112B in a firstpre-tensioned optic fiber extending along a z-axis. Mass 111 ispositioned between FBGs 113A and 113B in a second pre-tensioned opticfiber extending along an x-axis. Mass 111 is positioned between FBGs114A and 114B in a third pre-tensioned optic fiber extending along ay-axis. Each pair of FBGs along an axis functions in the same way as thepair of FBGs in FIG. 1A.

FIGS. 1C and 1D are illustrations of examples of flexural FBGaccelerometers. In a flexural FBG accelerometer, a FBG attached to aflexural beam stretches or compresses as the flexural beam flexes inresponse to accelerations of the inertial mass of the flexural beam or amass mounted on the beam exerting forces transverse to the fiber and theflexural beam.

In flexural FBG accelerometer 120, a first end of a tapered isoscelesplate 123 is clamped to an external frame 122 of accelerometer 120. Asecond end of tapered plate 123 is affixed to a seismic mass 123. Asingle optic fiber 121 extends through an opening in external frame 122,and is bonded to tapered plate 123 with an epoxy resin. The portion ofoptic fiber 121 bonded to tapered plate includes a FBG. Thus, as seismicmass 123 moves, tapered plate 123 is flexed, which in turn causes theFBG to stretch and un-stretch.

In another example of a flexural FBG accelerometer 130 (FIG. 1D), aportion of a single multi-core fiber 131 extends from a clamp 133. Fiber131 is affixed to clamp 133 that in turn is affixed to an end of a mainsensor housing 132. Only a portion of the main sensor housing is shownin FIG. 1D. FBGs 134 are included in the cores of fiber 131 andpositioned just outside collar 133. A mass 135 is attached to theunsupported end of fiber 131. Thus, the portion of fiber 131 with FBGs134 that extends from collar 133 is a cantilever beam.

FIG. 1E is a cross-sectional illustration of cores 131A, 131B, 131C,131D of fiber 131. Each of four cores 131A, 131B, 131C, 131D ispositioned at a different vertex of a square 136. The relative stretchand compression of FBGs in opposite cores of the fiber are measured todetermine the bending of fiber 131 in response to accelerations of mass135.

The third type of accelerometer (FIG. 1F) is a hybrid of the two formertypes of accelerometers. Hybrid accelerometer 140 includes a mass 141 onthe end of a beam 142. The combination of mass 141 and beam 142 acts viaa bell crank or lever to apply an axial load to stretch or un-stretchFBG 144 in optic fiber 143 in a manner similar to the axialaccelerometers described above.

The accelerometers described above are suitable for use in industrialapplications. However, in a teleoperated surgical application, a FBGbased accelerometer was not used. Instead, a micro-electro-mechanicalsystem (MEMS) accelerometer was used.

FIG. 1G is an illustration of a patient side cart 150 of a teleoperatedsurgical system. An instrument manipulator 152 is positioned at a distalend of a setup arm 151. A sterile adapter is mounted on instrumentmanipulator 152 and then a surgical instrument is mounted on the sterileadapter and instrument manipulator 152 combination. A MEMS accelerometerapparatus 155 is mounted just distal of a housing 154 of surgicalinstrument 153 on the distal portion of a surgical instrumentmanipulator 152.

Thus, considering the confined space and limited volume of the distalend of the surgical instrument tube of surgical instrument 153, MEMSaccelerometer apparatus 155 was mounted external to a patient andexternal to the surgical instrument tube of surgical instrument 153. Thesurgical instrument tube of surgical instrument 153 is sometimesreferred to as a shaft. MEMS accelerometer apparatus 155 is positionedexternal to the proximal end of the surgical instrument tube of surgicalinstrument 153. Also, a MEMS accelerometer was used in the teleoperatedsurgical application instead of the FBG accelerometers that be may beused in industrial applications.

SUMMARY

In one aspect, an accelerometer is included within the confined spaceand limited volume of a distal portion of a surgical instrument. Forexample, an apparatus includes a surgical instrument. The surgicalinstrument includes an end component, a joint coupled to the endcomponent, a shaft coupled to the joint, and an accelerometer positionedadjacent to and proximal to the joint.

In this aspect, the accelerometer includes a cantilever beam and anoptic fiber. The optic fiber includes a Fiber Bragg Grating, and theoptic fiber is affixed to the cantilever beam. In one aspect, theaccelerometer is included in a distal portion of the shaft.

In another aspect, the surgical instrument includes a force transducer.The force transducer includes the accelerometer, and the forcetransducer is mounted between a distal end of the shaft and the joint.Here, the optic fiber includes a second Fiber Bragg Grating. The secondFiber Bragg Grating is included in the force transducer, and the secondFiber Bragg Grating is positioned in the optic fiber between a proximalend of the optic fiber and the first Fiber Bragg Grating. The secondFiber Bragg Grating is used in measuring a force on the distal end ofthe surgical instrument.

In the accelerometer, the Fiber Bragg Grating is mounted on thecantilever beam a distance from a neutral axis of bending of thecombination of the cantilever beam and the optic fiber. In a furtheraspect, the cantilever beam has a first modulus of elasticity. The opticfiber has a second modulus of elasticity. In one aspect, the firstmodulus of elasticity is about equal to the second modulus ofelasticity. However, in other aspects, the first modulus of elasticitycan be up to three times the second modulus of elasticity.

The accelerometer includes a mass positioned at a free end of thecantilever beam. In one aspect, the mass is formed integrally with thecantilever beam. The cantilever beam is configured to deflect, inresponse to acceleration during a surgical procedure, a distancesufficient to strain the Fiber Bragg Grating so that the Fiber BraggGrating generates a measurable signal corresponding to the straininduced by acceleration of the mass. The cantilever beam also isconfigured to have a first mechanical resonance peak high enough to besufficient to permit measurement of the acceleration and to avoidcreating an unstable feedback around a low frequency force output deviceincluded in the apparatus. In one aspect, the accelerometer includes atravel stop configured to limit deflection of the cantilever beam.

The apparatus also includes a master control device coupled to thesurgical instrument, and a vibro-tactile haptic output device coupled tothe accelerometer and to the master control device. The vibro-tactilehaptic output device is configured to output momentary transientinformation and sustained time varying strain information acquired fromthe accelerometer either separately or in combination with the mastercontrol device.

The apparatus also includes a filter positioned after the accelerometerand before a vibro-tactile haptic output device and/or master controldevice. The filter is configured to limit the bandwidth of frequenciesoutput via the vibro-tactile haptic output device and/or the mastercontrol device. Optionally, the apparatus includes a sound systemcoupled to the accelerometer. The sound system is configured to generatean audible acoustic signal corresponding to the transient informationand the sustained time varying strain information acquired from theaccelerometer either separately or in combination.

Another aspect of the apparatus also includes a surgical instrument. Thesurgical instrument includes an end component, a joint coupled to theend component, a shaft coupled to the joint, and an accelerometerpositioned adjacent to and proximal to the joint.

The accelerometer is coupled to a distal portion of the shaft. Theaccelerometer includes a portion of a tube body and an optic fiber. Theoptic fiber includes a first portion and a second portion. The firstportion of the optic fiber is fixedly attached to the portion of thetube body. The second portion of the optic fiber is configured as acantilever beam. The second portion of the optic fiber includes theFiber Bragg Grating, and the second portion of the optic fiber extendsfrom the first portion of the optic fiber. In one aspect, the tube bodyis a distal portion of the shaft.

In one aspect, the tube body is a tube body of a force transducer. Theforce transducer is positioned between the distal end of the shaft andthe joint. The optic fiber further includes a second Fiber BraggGrating. The second Fiber Bragg Grating is included in the forcetransducer, and the second Fiber Bragg Grating is positioned between aproximal end of the optic fiber and the first portion of the opticfiber. The second Fiber Bragg Grating is used in measuring a force onthe distal end of the surgical instrument.

In one aspect, the accelerometer includes a mass attached to a free endof the second portion of the optic fiber. The second portion of theoptic fiber is configured to deflect, in response to acceleration duringa surgical procedure, a distance sufficient to strain the first FiberBragg Grating so that the first Fiber Bragg Grating generates ameasurable signal corresponding to the strain induced by theacceleration of the mass. The second portion of the optic fiber also isconfigured to have a first mechanical resonance peak high enough to besufficient to permit measurement of the acceleration and to avoidcreating an unstable feedback around a force output device included inthe apparatus.

In another aspect, the portion of the tube body includes an aperture.The second portion of the optic fiber and the mass are positioned in theaperture. In some aspects, the accelerometer also includes a travel stopconfigured to limit deflection of the cantilever beam.

The apparatus also includes a master control device coupled to thesurgical instrument, and a vibro-tactile haptic output device coupled tothe accelerometer and to the master control device. The vibro-tactilehaptic output device is configured to output transient information andsustained time varying strain information acquired from theaccelerometer either separately or in combination on the master controldevice.

The apparatus also includes a filter positioned after the accelerometerand before the vibro-tactile haptic output device and/or master controldevice. The filter is configured to limit the bandwidth of frequenciesoutput via the vibro-tactile haptic output device and/or master controldevice. Optionally, the apparatus includes a sound system coupled to theaccelerometer. The sound system is configured to generate an audibleacoustic signal corresponding to the transient information and thesustained time varying strain information acquired from theaccelerometer either separately or in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a prior art axial Fiber Bragg Grating accelerometer.

FIG. 1B illustrates a prior art tri-axial Fiber Bragg Gratingaccelerometer.

FIGS. 1C and 1D illustrate examples of prior art flexural Fiber BraggGrating accelerometers.

FIG. 1E is a cross-sectional illustration of the optic fiber in theaccelerometer of FIG. 1D.

FIG. 1F illustrates a prior art hybrid Fiber Bragg Gratingaccelerometer.

FIG. 1G illustrates a prior art patient side cart of a teleoperatedsurgical system that includes a surgical instrument with a MEMSaccelerometer positioned near a distal portion of the surgicalinstrument manipulator.

FIG. 2 is a high-level diagrammatic view of a teleoperated surgicalsystem including an accelerometer mounted on a distal portion of asurgical instrument and including vibro-tactile feedback.

FIG. 3A is a perspective illustration of a surgical instrument thatincludes a force sensor and accelerometer apparatus at a distal portionof the surgical instrument.

FIG. 3B is an enlarged diagram of one aspect of force sensor andaccelerometer apparatus of FIG. 3A.

FIG. 3C is an illustration of a portion of another surgical instrumentthat includes the accelerometer on a joint.

FIG. 3D is an illustration of a portion of yet another surgicalinstrument that includes the accelerometer on an end component.

FIG. 4A is an illustration of a portion of a surgical instrument bodythat includes an accelerometer with a cantilever beam and an optic fiberaffixed to the cantilever beam. The optic fiber includes a Fiber BraggGrating positioned near the fixed end of the cantilever beam.

FIG. 4B is an illustration of a portion of a surgical instrument bodythat includes an accelerometer with an optic fiber including Bragg FiberGratings configured as a cantilever beam.

FIG. 4C is a cross-sectional illustration of the optic fiber in theaccelerometer of FIG. 4B.

FIG. 5A is an alternative implementation of the accelerometer of FIG.4A.

FIG. 5B is an alternative implementation of the accelerometer of FIG.4B.

FIG. 6A is an illustration of another aspect of a distal portion of asurgical instrument that includes a force sensor and accelerometerapparatus.

FIG. 6B is an enlarged view of the distal end of the force sensor andaccelerometer apparatus of FIG. 6A.

FIG. 6C is an enlarged view of the accelerometer of FIGS. 6A and 6B.

FIG. 7A is a diagram of yet another aspect of a distal portion of asurgical instrument that includes a force sensor and accelerometerapparatus where the optic fiber is configured as a cantilever beam.

FIG. 7B is an enlarged view of the accelerometer of FIG. 7A.

FIG. 8 is a block diagram illustrating the processing of the informationgenerated by each of the force sensor and accelerometer apparatusesdescribed herein.

FIG. 9 is an illustration of a master tool manipulator that includes abase, a master tool grip, and a vibro-tactile feedback module coupled tothe master tool grip.

In the drawings, the first digit of a reference numeral indicates thefigure number in which an element having that reference numeral firstappears.

DETAILED DESCRIPTION

In one aspect of this invention, a small accelerometer is included on adistal portion of a surgical instrument. Unlike MEMS accelerometers thathave been previously used on a part of a surgical instrument manipulatorthat is external to a patient and well removed from the distal end ofthe surgical instrument, the accelerometer is positioned near or on thedistal tip of the surgical instrument. Thus, during a clinicalprocedure, the accelerometer is positioned within the patient near thesource of the interaction between the teleoperated surgical instrumentand the surgical working environment that produces the high frequencycontent that excites the accelerometer.

Herein, two frequency ranges are of interest. The first frequency rangeincludes low frequency content (zero to thirty Hertz (Hz)) associatedwith interactions between the teleoperated surgical instrument and thesurgical working environment. The second frequency range includes highfrequency content (thirty to one thousand Hz) associated with theinteraction between the teleoperated surgical instrument and thesurgical working environment.

The high frequency content detected by the accelerometer is filtered andvibro-tactile feedback is provided to the person operating the surgicalinstrument, and in some instances to others in the operating theater.For example, the master tool grip used to operate the slave surgicalinstrument is vibrated in direct correlation to the high frequencycontent detected by the accelerometer.

This feedback enables a surgeon to experience the interaction betweenthe teleoperated surgical instrument and the surgical workingenvironment, including for example, a suture needle being handed betweeninstruments, a needle being passed thru tissue, incidental contactbetween instruments, and the like. The high frequency content may alsobe thought of as clicks, bumps or momentary forces and impacts asopposed to smoother, slower changing or sustained forces associated withthe low frequency content. The high frequency content of the interactionbetween the teleoperated surgical instrument and the surgical workingenvironment includes sustained time varying information as well asshorter transient information.

The higher frequency content of mechanical interactions is better sensedby an accelerometer than a force sensor. The high frequency content ofthe interaction between the teleoperated surgical instrument and thesurgical working environment is output to the surgeon by, for example,the inertial reaction force of a voice coil moving a small counter massclosely coupled to a master tool grip. (See FIG. 9) The surgeon graspsthe master tool grip to move the teleoperated surgical instrument. Thehigh frequency content of the interaction between the teleoperatedsurgical instrument and the surgical working environment is distinctfrom the lower frequency content that is better suited to be output tothe surgeon by forces exerted on his/her hands by the master control armto which the master tool grip is attached.

While the use of accelerometers and in particular Fiber Bragg Gratingaccelerometers were known, their use was typically in industrialapplications that were not constrained by the space, size, andenvironmental constraints associated with the distal end of a surgicalinstrument. As discussed above, the use of any accelerometer on thedistal end of a surgical instrument apparently was consideredinfeasible, because a MEMS accelerometer apparatus was used near theproximal end of the surgical instrument.

There is very little available volume at the distal end of a surgicalinstrument and any wiring must be routed alongside the cables used toactuate the surgical instrument. In addition to the mechanical forcesassociated with the actuation cables, there is strong electricalinterference associated with the use of cautery. Also, there may bethermal gradients as the illumination used in the surgery may heat onlyone side of the instrument.

In one aspect, a Fiber Bragg Grating accelerometer is positioned on thedistal portion of the surgical instrument, e.g., proximal to a wristjoint of the surgical instrument. In one aspect, the Fiber Bragg Gratingaccelerometer takes advantage of optic fibers routed to the distal endof the surgical instrument for low frequency force sensing. The FiberBragg Grating accelerometer is immune to electric noise, and since theoutput of the accelerometer is high pass filtered, slower or DCtemperature effects on the performance of the Fiber Bragg Grating arenot of concern.

In one aspect, as described more completely below, an optic fiber usedin low frequency force sensing is extended and mounted on a cantileverbeam, or alternatively the optic fiber itself functions as thecantilever beam. When a cantilever beam is used, a Fiber Bragg Gratingin the optic fiber is positioned near a first end of the cantilever beamand at a second end of the cantilever beam typically is a mass. Thefirst end of the cantilever beam is fixed in place and so is referred toas the fixed end of the cantilever beam. The second end of thecantilever beam is not fixed in place and is free to move. Thus, thesecond end of the cantilever beam is referred to as the free end of thecantilever beam.

High frequency content of the interaction between the teleoperatedsurgical instrument and the surgical working environment causes the masson the second end of the cantilever beam to move. The movement of themass flexes the cantilever beam, which is turn strains the Fiber BraggGrating. The strain in the Fiber Bragg Grating causes a location of acenterline of a light wavelength peak reflected by the Fiber BraggGrating to shift from the location of the centerline when the FiberBragg Grating is unstrained. The shift of the centerline location isconverted to strain information. The strain information is used toprovide vibro-tactile feedback to the surgeon, as explained below, onthe high frequency content of the interaction between the teleoperatedsurgical instrument and the surgical working environment.

FIG. 2 is a high-level diagrammatic view of a teleoperated surgicalsystem 200, for example, the minimally invasive teleoperated da Vinci®Surgical System, including an accelerometer mounted on a distal portionof surgical instrument 215. (da Vinci® is a registered trademark ofIntuitive Surgical, Inc. of Sunnyvale, Calif.) The accelerometer in notshown because the distal portion of surgical instrument 215 thatincludes the accelerometer is within patient 211.

In this example, a surgeon, using master controls at a surgeon's console260, remotely manipulates an endoscope 212 mounted on a teleoperatedmanipulator arm 213 of patient-side cart 210. The surgeon also canremotely manipulate one or more surgical instruments mounted onteleoperated arms of patient-side cart 210. The surgical instrumentsinclude surgical instrument 215 that is mounted on teleoperatedmanipulator arm 214.

There are other parts, cables, etc. associated with the da Vinci®Surgical System, but these are not illustrated in FIG. 2 to avoiddetracting from the disclosure. Further information regarding minimallyinvasive surgical systems may be found for example in U.S. patentapplication Ser. No. 11/762,165 (filed Jun. 23, 2007; disclosingMinimally Invasive Surgical System), U.S. Pat. No. 6,837,883 B2 (filedOct. 5, 2001; disclosing Arm Cart for Telerobotic Surgical System), andU.S. Pat. No. 6,331,181 (filed Dec. 28, 2001; disclosing SurgicalRobotic Tools, Data Architecture, and Use), all of which areincorporated herein by reference.

In this aspect, an accelerometer is mounted on the distal portion ofsurgical instrument 215. The accelerometer is positioned proximal to andadjacent to a wrist joint. The accelerometer includes a cantilever beamand an optic fiber. The optic fiber is fixedly attached to a side of thecantilever beam. The optic fiber includes a first Fiber Bragg Grating.The first Fiber Bragg Grating is positioned adjacent a fixed end of thecantilever beam. In one aspect, the optic fiber also includes a secondFiber Bragg Grating. The second Fiber Bragg Grating is part of a forcesensor.

The optic fiber is coupled to an interrogator unit 220. Interrogatorunit 220 decodes the optically encoded acceleration information from theaccelerometer into electrical signals compatible with the computercontrol hardware in system controller 230.

System controller 230 represents the various controllers in system 200.System controller 230 sends control commands to the slave surgicalinstrument in response to control commands. The control commands arebased on movements of the masters in surgeon's control console 260 bysurgeon 261. A display module 232 in system controller 230 also updatesa stereoscopic view 262 of the surgical site generated by the displaydevice in surgeon's control console 260 as the slave surgical instrumentmoves in response to the control commands. The control of the surgicalinstruments and the display of stereoscopic images is the same as inprior systems, except with respect to the vibro-tactile feedback asindicated herein, and so are not considered in further detail.

Although described as system controller 230, it is to be appreciatedthat system controller 230 may be implemented in practice by anycombination of hardware, software that is executed on a processor, andfirmware. Also, its functions, as described herein, may be performed byone unit, or divided up among different components, each of which may beimplemented in turn by any combination of hardware, software that isexecuted on a processor, and firmware. When divided up among differentcomponents, the components may be centralized in one location ordistributed across system 200 for distributed processing purposes.

The signals from interrogator 220 are processed by a vibro-tactilefeedback module 231 in system controller 230. As explained morecompletely below, vibro-tactile feedback module 231 filters the signalsfrom interrogator 220 and then sends output signals to a vibro-tactilefeedback device mounted on the master tool grip in surgeon's controlconsole 260. In response to the filtered signals, the vibro-tactilefeedback device causes the master tool grip in the console 260 tovibrate in relation to the high frequency content of the interactionbetween the teleoperated surgical instrument and the surgical workingenvironment detected by the accelerometer. Thus, surgeon 261 receivesvibro-tactile feedback 263. In addition, vibro-tactile feedback module231 can send another signal to an audible feedback device that in turngenerates an audio sound corresponding to the high frequency content ofthe interaction between the teleoperated surgical instrument and thesurgical working environment detected by the accelerometer.Vibro-tactile feedback module 231 may also generate signals that aresent to other components in the system controller. The audible feedback,vibro-tactile feedback, and system controller then provide informationto surgeon 261 about the surgical instruments that enhances thesurgeon's ability to perform the surgical procedure.

FIG. 3A is a perspective illustration of a surgical instrument 300.Arrow 395 shows the proximal direction and the distal direction in FIG.3A.

Surgical instrument 300 includes a housing 301, a shaft 302, a forcesensor and accelerometer apparatus 303, a joint 304, and an endcomponent 305. End component 305, such as a surgical end effector, iscoupled to force sensor and accelerometer apparatus 303 via joint 304,e.g., a wrist joint. Force sensor and accelerometer apparatus 303 iscoupled to a distal end of a shaft 302 and is coupled to joint 304 inthis aspect. Housing 301 is operably coupled to a proximal end of shaft302, and housing 301 includes an interface which mechanically,electrically, and optically couples instrument 300 to an instrumentmanipulator assembly.

In one aspect of FIG. 3A, force sensor and accelerometer apparatus 303is a separately manufactured unit that is coupled between the distal endof shaft 302 and joint 304 and that becomes part of shaft 302. In thisaspect, force sensor and accelerometer apparatus 303 includes an outercover that is seen in FIG. 3A. In another aspect, force sensor andaccelerometer apparatus 303 is formed on a distal end portion shaft andis not a separately manufactured unit.

FIG. 3B is an enlarged diagram of one aspect of force sensor andaccelerometer apparatus 303, sometimes referred to as apparatus 303.Apparatus 303 includes a force sensor and at least one accelerometer320Y. Apparatus 303 includes a generally annular tube 306 operablycoupled to a distal end of shaft 302 and operably coupled to a proximalbody segment of joint 304. In one aspect, shaft 302 is a rigid shaft.

In this aspect, tube 306 includes a number of rectangular-shapedapertures 307 cut from tube 306 and a plurality of radial ribs 308forming through passages for passage of actuation cables, wires, tubes,rods, and/or flushing fluids through tube 306. Each of plurality ofradial ribs 308 extends lengthwise in a direction of the lengthwise axisof tube 306, the z-axis, and each radial rib of the plurality of radialribs extends radially along a radius of tube 306 from the z-axiscenterline of tube 306.

Also, in this aspect, a number of optic fibers 310, e.g., four opticfibers, are mounted on an outer surface of tube 306. In FIG. 3B, thefour optic fibers are equally spaced, 90 degrees apart, around the outersurface of tube 306, and only two of the four optic fibers are visiblein FIG. 3B. The ninety-degree spacing is illustrative only and is notintended to be limiting. For examples of other spacings between theoptic fibers, see U.S. Patent Application Publication No. US2009/0157092 A1 (filed Dec. 18, 2007), which is incorporated byreference.

Optic fibers 310 may be inlaid in grooves 311 that form part of theouter surface of tube 306, or in a depressed area that forms part of theouter surface of tube 306. In this example, the outer surface of shaft302 also includes a plurality of grooves 314 for optic fibers 310.

Some of optic fibers 310 include three strain gauges 309, while othersof optic fibers 310 include two strain gauges. In one aspect, the straingauges 309 utilize Fiber Bragg Gratings. In FIG. 3B, each of the twovisible optic fibers include three strain gauges, while each of the twooptic fibers that are not visible include two strain gauges. The use ofa particular number of strain gauges in each optic fiber is illustrativeonly and is not intended to be limiting. An optic fiber may contain oneor more strain gauges.

A first set of strain gauges 309 are spaced equally, ninety degreesapart, around the outer surface of tube 306 at a first axial position sothat the first set of strain gauges 309 form a first ring 312 of straingauges. A second set of strain gauges 309 are spaced equally, ninetydegrees apart, around the outer surface of tube 306 at a second axialposition so that the second set of strain gauges 309 form a second ring313 of strain gauges.

Each of strain gauges 309 in first ring 312 and in second ring 313 areoriented parallel to the lengthwise z-axis of tube 306 and are mountedon the outer surface over a rib 308 and between two apertures. If tube306 did not include apertures, each of strain gauges 309 in first ring312 and in second ring 313 are oriented parallel to the lengthwisez-axis of tube 306 and are mounted on the outer surface over a rib 308.

First ring of strain gauges 312 is mounted at a chosen distance fromsecond ring of strain gauges 313 and the two rings are aligned so thatstrain gauges in a pair of stain gauges in the two rings are alignedwith each other along the lengthwise z-axis. Low frequency forcesapplied to distal portions 305 and 304 along the X-axis and Y-axis canbe determined using the plurality of strain gauges in rings 312 and 313.See U.S. Pat. No. 8,375,808 B2, which is incorporated by reference.

In this aspect, force sensor and accelerometer apparatus 303 includestwo accelerometers 320Y and 320X. An optic fiber 310 extends from theforce sensor unto a cantilever beam 315 with strain gauge 309 positionednear the fixed end of cantilever beam 315 in each of accelerometers 320Yand 320X. Accelerations in the Y-direction cause cantilever beam 315 ofaccelerometer 320Y to flex in the Y-direction, which in turn strainsstrain gauge 309. Thus, optic fiber 310 carries strain information formeasurement of low frequency forces and strain information formeasurement of high frequency accelerations.

In FIG. 3B, accelerometers 320X and 320Y are proximal to joint 304.However, in other aspects, the accelerometer or accelerometers are onjoint 304 or on end component 305.

For example, in FIG. 3C, a portion of a different surgical instrumentincludes shaft 302, force sensor apparatus 303C, a joint 304C withaccelerometer 320C, and end component 305. End component 305 is coupledto force sensor apparatus 303C via joint 304C, e.g., a wrist joint.Force sensor apparatus 303C is coupled to a distal end of a shaft 302and is coupled to joint 304C in this aspect. In FIG. 3C, components witha reference numeral the same as a reference numeral in an earlierdrawing are equivalent to components described with respect to theearlier drawings, and so that description is not repeated here.

Force sensor apparatus 303C includes two rings of strain gauges similarto rings 312 and 313 that were described above. Accelerometer 320C ispositioned in a short body segment of joint 304C that is coupled to thedistal end of force sensor apparatus 303C. Accelerometer 320C includes astrain gauge. The strain gauge can be in an extension of one of theoptic fibers in force sensor apparatus 303C or can be in a dedicatedoptic fiber.

In FIG. 3D, a portion of yet another surgical instrument includes shaft302, force sensor apparatus 303C, a wrist joint 304, and end component305D. End component 305D includes an accelerometer 320D in one of thejaws of end component 305D. End component 305D is coupled to forcesensor apparatus 303C via joint 304, e.g., a wrist joint. Force sensorapparatus 303C is coupled to a distal end of a shaft 302 and is coupledto joint 304 in this aspect. In FIG. 3D, components with a referencenumeral the same as a reference numeral in an earlier drawing areequivalent to components described with respect to the earlier drawings,and so that description is not repeated here.

Accelerometer 320D includes a strain gauge. The strain gauge can be inan extension of one of the optic fibers in force sensor apparatus 303Cor can be in a dedicated optic fiber. The optic fiber including thestrain gauge of accelerometer 320D runs axially thru the instrument andintersects the transverse axis of a wrist pivot shaft (with a gap in theshaft for the fiber) when wrist joint 304 is in its neutral position.The optic fiber can move and bend without length change when wrist joint304 pivots back and forth.

FIGS. 4A and 4B are illustrations of alternative implementations of acantilever beam accelerometer with a Fiber Bragg Grating in an opticfiber that is positioned on a distal portion of surgical instrument 300.Accelerometer 420A (FIG. 4A) is formed in a wall of an annular tube,e.g., is formed on a portion of a body 406A. Accelerometer 420A includesa cantilever beam 415A and an optic fiber 410A. In this aspect, a firstend 415A1 of cantilever beam 415A extends from body 406A in a directionof a lengthwise axis 419A. A mass 416A is attached to a second end 415A2of cantilever beam 415A. In this aspect, cantilever beam 415A and mass416A are a single integrated part. Cantilever beam 415A and mass 416Aare positioned in an opening through a wall of body 406A.

An outer surface 407A of body 406A includes a groove 411A or a depressedregion. An optic fiber 410A including a Fiber Bragg Grating 409A isaffixed in, e.g., epoxied in, groove 411A. Fiber Bragg Grating 409A ispositioned adjacent fixed end 415A1 of cantilever beam 415A. In thisaspect, optic fiber 410A has a single core that includes Fiber BraggGrating 409A.

Cantilever beam 415A with mass 416A is configured to have adequatedeflection at accelerations experienced during surgical activities toprovide a strain in Fiber Bragg Grating 409A. The strain is measurablewith adequate signal to noise ratio for the resolution and the range ofexpected accelerations. In one aspect, content in a frequency range of30 Hz to 1000 Hz are of interest, and more particularly content in afrequency range of 50 Hz to 200 Hz. The frequency range is selected sothat realistic feedback can be provided to the surgeon with theparticular surgical robot master control arm and/or master arm surgeonhandgrip on surgeon's control console 260.

Also, cantilever beam 415A with mass 416A is configured to have a firstmechanical resonance peak above the frequency content of the surgicalactivities and above that of any vibration induced accelerations andforces originating in the surgical robot, the support assembly of thesurgical robot, and attached equipment. Also, the first mechanicalresonance peak is sufficiently high to avoid creating an unstablefeedback loop around any low frequency force output device attached tothe surgical robot master control arm or to the master control armsurgeon handgrip. As is known to those knowledgeable in the field, todetermine the resonance characteristics of the cantilever beam, the beamdesign typically is first modeled, either with hand calculations or acomputer based finite element analysis, and then verified withexperimental analysis.

Finally, in one aspect, cantilever beam 415A with mass 416A isconfigured to withstand mechanical shock (e.g. if the instrument isdropped on a floor) or excessively high intensity vibration (e.g. ifbeam 415A is excited by an unstable feedback control loop) either by itsown strength or by an over travel stop feature(s) limiting deflection ofcantilever beam 415A. Thus, in one aspect, accelerometer 420A includes amechanical stop 417A to limit the range of motion of cantilever beam415A in the direction towards the centerline axis 419A of body 406A. Thesidewalls of the opening in body 406A surrounding cantilever beam 415Aand mass 416A function as a mechanical stop also.

To obtain a good signal-to-noise ratio, several aspects of Fiber BraggGrating 409A and optic fiber 410A are considered. First, optic fiber410A with Fiber Bragg Grating 409A is mounted as far as possible from aneutral axis of bending 418A of the combination of cantilever beam 415Aand optic fiber 410A to produce the greatest strain and strongestsignal. As used herein, neutral axis of bending 418A is an axis alongthe length of cantilever beam 415A, which remains unstressed, neithercompressed nor stretched when cantilever beam 415A is bent.

In one aspect, optic fiber 410A is a silica glass fiber and cantileverbeam 415A is made of a high strength aluminum alloy (e.g., 7075-T6aluminum). The modulus of elasticity of silica glass and the modulus ofelasticity of the high strength aluminum alloy are both about 10,500ksi. Thus, as shown in FIG. 4A, when optic fiber 410A is mounted ingroove 410A in outer surface 407A of body 406A, neutral axis of bending418A of the combination of cantilever beam 415A and optic fiber 410A isapproximately the neutral axis of bending of cantilever beam 415A. Thus,optic fiber 410A with Fiber Bragg Grating 409A is displaced from neutralaxis of bending 418A. In general, the fiber core with the Fiber BraggGrating is located offset from the neutral axis of bending so that theFiber Bragg Grating has axial strain when the beam bends in response tolateral accelerations of the instrument tip. This is true if the fibercore is offset from the beam's neutral axis, and the smaller the fibermodulus of elasticity compared to the beam modulus of elasticity, themore the beam dominates in the neutral axis of the combined assembly.

Another aspect affecting the quality of the reflected signal from FiberBragg Grating 409A is the length of Fiber Bragg Grating 409A. In thisaspect, interrogator 220 detects a spectral location of a wavelengthpeak of the reflected light. If the length of Fiber Bragg Grating 409Ais too short, a broader peak of reflected light is obtained and thestrain induced offset of the wavelength peak is a smaller fraction ofthe peak width resulting in less certain peak shift measurement and apoorer signal to noise ratio.

The strain at any point along Fiber Bragg Grating 409A is a function ofthe bending moment on the cantilever beam at that point and thereforedepends on the distance between mass 416A and that point of Fiber BraggGrating 409A. Thus, Fiber Bragg Grating 409A experiences a range ofstrains and reflects light of a range of wavelengths. If the length ofFiber Bragg Grating 409A is too large a fraction of the length of thecantilever beam 415A, the detected wavelength peak is broader due tochirp. Chirp is the variation of strain along Fiber Bragg Grating 409A.Again, the strain induced offset of the wavelength peak is a smallerfraction of the peak width resulting in less certain peak shiftmeasurement and a poorer signal to noise ratio.

Thus, the length of Fiber Bragg Grating 409A is selected so that thepeak broadening effects of a shorter length and of the chirp inducedbroadening in a longer length Fiber Bragg Grating on an end loadedcantilever beam are of similar magnitude and the overall peak broadeningeffect is minimized. This allows interrogator 220 to more accuratelydetermine the location of the peak in both the strained and unstrainedstates so that the difference in the locations of the peaks can be usedto ascertain the acceleration experienced by cantilever beam 415A.

Accelerometer 420B (FIG. 4B) includes an outer surface 407B of a body406B and an optic fiber 410B. Optic fiber 410B includes Fiber BraggGratings 409B. The location of the light conducting cores and FiberBragg Gratings with respect to the neutral axis of bending of the fiberoptic cantilever beam is described below. Body 406B is, for example, anannular tube.

In this aspect, a first portion of the optic fiber 410B is fixedlyattached, e.g., epoxied, in a groove 411B or a depressed region insurface 407B. The first portion of the optic fiber 410B is adjacent to,but does not include Fiber Bragg Gratings 409B.

A second portion of optic fiber 410B extends from the first portion andis configured as cantilever beam 415B. The second portion of optic fiber410B includes Fiber Bragg Gratings 409B.

In this aspect, a first end 415B 1 of cantilever beam 415B extends awayfrom body 406B in a direction of a lengthwise axis into an opening 421Bthrough a wall of body 406B. A mass 416B is attached to a second end415B2 of cantilever beam 415B.

Fiber Bragg Gratings 409B are positioned adjacent first end 415B1 ofcantilever beam 415B. Typically, when optic fiber 410B is epoxied ingroove 411B, an epoxy meniscus is formed around optic fiber 410B. Theepoxy meniscus extends into opening 421B. Thus, the start of cantileverbeam 415B is not coincident with the edge of opening 421B in this case.The effect of the epoxy meniscus is considered when positioning FiberBragg Gratings 409B prior to affixing optic fiber 410B in groove 411B sothat Fiber Bragg Gratings 409B are near first end 415B of cantileverbeam 415B, but not exactly at first end 415B of cantilever beam 415.

Herein, when it said that a Fiber Bragg Grating is positioned near anend of a cantilever beam or adjacent a fixed end of a cantilever beam,it means that the Fiber Bragg Grating is positioned so that when thecantilever beam deflects, all of the Fiber Bragg Grating is strained. Ifthe Fiber Bragg Grating is positioned too close to the first end of thecantilever beam, a portion of the Fiber Bragg Grating would not bestrained when the cantilever beam deflects and so the Fiber BraggGrating would be further chirped, which broadens the reflected lightpeak, as described above. Similarly, if the Fiber Bragg Grating ispositioned too far from the first end of the cantilever beam, the momentarm between the Fiber Bragg Grating and the effect of the mass isdiminished, which diminishes the response of the accelerometer. Thus,the Fiber Bragg Grating is placed as close as possible to the first endof the cantilever beam without incurring chirping due to an unstrainedportion of the Fiber Bragg Grating.

In this aspect, optic fiber 410B is a multi-core fiber. FIG. 4C is across-sectional illustration of cores 410B 1, 410B2, and 410B3 of opticfiber 410. Each of cores 410B1, 410B2, and 410B3 is positioned at adifferent vertex of an equilateral triangle 436 centered on a crosssection of optic fiber 410B. The black dot in FIG. 4C represents neutralaxis of bending 418B, which is also the centerline axis of optic fiber410B.

FIG. 4C shows that each of cores 410B 1, 410B2, and 410B3 is displacedfrom centerline neutral axis of bending 418B. Also, each of cores 410B1,410B2, and 410B3 includes a Fiber Bragg Grating. Herein, a singlecantilever beam 415B is described, but actually each of the three coresundergoes strain when cantilever beam 415B is deflected. Thus, bycombining the strains from all three Fiber Bragg Gratings, cantileverbeam 415B can provide the magnitude and direction of accelerations inall transverse directions. In one aspect, a matrix known to thoseknowledgeable in the field is used to transform the three strain signalsinto acceleration.

Again, cantilever beam 415B with mass 416B is configured to haveadequate deflection at accelerations experienced during surgicalactivities to provide a strain in two or three of Fiber Bragg Gratings409B. The strain is measurable with adequate signal to noise ratio forthe resolution and the range of expected accelerations. In one aspect,frequencies in a range of 30 Hz to 1000 Hz are of interest, and moreparticularly frequencies in a range of 50 Hz to 200 Hz. The range offrequencies is selected so that realistic feedback can be provided tothe surgeon with the particular surgical robot master control arm andmaster arm surgeon handgrip on surgeon's control console 260.

Also, cantilever beam 415B with mass 416B is configured to have a firstmechanical resonance peak above the frequency content of the surgicalactivities and above that of any vibration induced accelerations andforces originating in the surgical robot, the support assembly of thesurgical robot and attached equipment. Also, the first mechanicalresonance peak is sufficiently high to avoid creating an unstablefeedback loop around any force output device attached to the surgicalrobot master control arm or to the master arm surgeon handgrip. Again,as is known to those knowledgeable in the field, to determine theresonance characteristics of the cantilever beam, the beam designtypically is first modeled, either with hand calculations or a computerbased finite element analysis, and then verified with experimentalanalysis.

Finally, in one aspect, cantilever beam 415B with mass 416B isconfigured to withstand mechanical shock (e.g. if the instrument isdropped on a floor) or excessively high intensity vibration (e.g. ifcantilever beam 415B is excited by an unstable feedback control loop)either by its own strength or by an over travel stop feature(s) limitingdeflection of cantilever beam 415B. Thus, in one aspect, accelerometer420B includes a mechanical stop 417B to limit the range of motion ofcantilever beam 415B in the direction towards the centerline of body406B. The sidewalls of the opening surrounding cantilever beam 415B andmass 416B function as a mechanical stop also.

To obtain a good signal-to-noise ratio, the cores with Fiber BraggGratings 409B are mounted as far as possible from a neutral axis ofbending 418B of the cantilever beam 415B portion of optic fiber 410B toproduce the best signal. Another aspect affecting the quality of thereflected signal from Fiber Bragg Grating 409B is the length of FiberBragg Gratings 409B. In this aspect, interrogator 220 detects shifts inthe locations of respective wavelength peaks of the reflected light. Ifthe length of Fiber Bragg Gratings 409B is too short, broader peaks ofreflected light are obtained relative to the wavelength shift and thesignal to noise ratio of the output from interrogator 220 is poorer.

The strain on each of Fiber Bragg Gratings 409B is a function of thedistance between mass 416B and that Fiber Bragg Grating. Thus, if eachof Fiber Bragg Gratings 409B is too long, different parts of that FiberBragg Grating experience different strains and so reflect light having abroader spectrum of wavelengths, i.e., the Fiber Bragg Grating ischirped. This again results in a broader reflected peak of light thatdoes not have as clear a peak, and so again the output of interrogator220 has a poorer signal to noise ratio.

Thus, the length of Fiber Bragg Gratings 409B is selected so that inunstrained and strained states the Fiber Bragg Grating provides areflected light wavelength peak with a definitive peak location. Thisallows interrogator 220 to accurately determine the location of the peakin both the unstrained and strained states so that the difference in thepeak locations can be used to ascertain the acceleration experienced bycantilever beam 415B.

In the above examples of a cantilever beam accelerometer at the distalend of a surgical instrument, the free end of the cantilever beam wasdistal to the fixed end of the cantilever beam. This is illustrativeonly and is not intended to be limiting. FIG. 5A is a diagram of oneaspect of a portion of a force sensor and accelerometer apparatus 503A,sometimes referred to as apparatus 503A. Apparatus 503A includes a forcesensor and at least one accelerometer 520A. Apparatus 503A includes agenerally annular tube 506A that can be operably coupled to a distal endof shaft 302 and that can be operably coupled to a proximal body segmentof joint 304. In one aspect, shaft 302 is a rigid shaft.

In this aspect, tube 506A does not include a number ofrectangular-shaped apertures, but does include a plurality of radialribs forming through passages for passage of actuation cables, wires,tubes, rods, and/or flushing fluids. The plurality of radial ribs areequivalent to plurality of radial ribs 308 that was described above, andso instead of repeating the description, the description of plurality ofradial ribs 308 is incorporated by reference.

Again, in this aspect, a number of optic fibers 510A1, 510A2, e.g., fouroptic fibers, are mounted on an outer surface of tube 506A. The fouroptic fibers are spaced equally, 90 degrees apart, around outer surface507A of tube 506A, but only portions of two of the four optic fibers areshown in FIG. 5A. The ninety-degree spacing is illustrative only and isnot intended to be limiting. For examples of other spacings between theoptic fibers, see U.S. Patent Application Publication No. US2009/0157092 A1 (filed Dec. 18, 2007).

Each of optic fibers 510A1, 510A2 includes at least one strain gauge509A1, 509A2 that is used in low frequency force sensing, as describedwith respect to FIG. 3B. Optic fibers 510A1, 510A2 may be inlaid ingrooves that form part of outer surface 507A of tube 506A, or in adepressed area that forms part of outer surface 507A of tube 506A.

In this aspect, force sensor and accelerometer apparatus 503A includesat least one accelerometer 520A. Optic fiber 510A1 extends unto acantilever beam 515A with strain gauge 509A5 positioned near a fixed end515A1 of cantilever beam 515A. Thus, optic fiber 510A carries straininformation for measurement of low frequency forces and straininformation for measurement of accelerations.

In this aspect, cantilever beam 515A extends from first end 515A1 in aproximal direction away from a distal end of body 506A towards secondend 515A2. Second end 515A2 is the free end of cantilever beam 515A andis connected to mass 516A. Thus, in this example, second end 515A2 ofcantilever beam 515A is proximal to first end 515A1 of cantilever beam515A. The distal and proximal directions are represented by arrow 595.The design and function of accelerometer 520A is equivalent to thatdescribed above with respect to accelerometer 420A.

FIG. 5B is a diagram of one aspect of a portion of a force sensor andaccelerometer apparatus 503B, sometimes referred to as apparatus 503B.Apparatus 503B includes a force sensor and at least one accelerometer520B. Apparatus 503B includes a generally annular tube 506B that can beoperably coupled to a distal end of shaft 302 and that can be operablycoupled to a proximal body segment of joint 304. In one aspect, shaft302 is a rigid shaft.

In this aspect, tube 506B does not include a number ofrectangular-shaped apertures, but does include a plurality of radialribs forming through passages for passage of actuation cables, wires,tubes, rods, and/or flushing fluids. The plurality of radial ribs areequivalent to plurality of radial ribs 308 that was described above, andso instead of repeating the description, the description of plurality ofradial ribs 308 is incorporated by reference.

Again, in this aspect, four optic fibers are mounted on an outer surface507B of tube 506B. The four optic fibers are equally spaced, 90 degreesapart, around outer surface 507A of tube 506A, but only portions of twoof the four optic fibers are shown in FIG. 5B. The ninety-degree spacingis illustrative only and is not intended to be limiting. For examples ofother spacings between the optic fibers, see U.S. Patent ApplicationPublication No. US 2009/0157092 A1 (filed Dec. 18, 2007).

Each of optic fibers 510B1, 510B2 includes at least one strain gauge509B1, 509B2 that is used in low frequency force sensing, as describedwith respect to FIG. 3B. Optic fibers 510B1, 510B2 may be inlaid ingrooves that form part of outer surface 507B of tube 506B, or in adepressed area that forms part of outer surface 507B of tube 506B.

In this aspect, force sensor and accelerometer sensor apparatus 503Bincludes at least one accelerometer 520B. A first portion of the opticfiber 510B1 is fixedly attached, e.g., epoxied, in a groove or adepressed region in surface 507B. The first portion of the optic fiber510B1 is adjacent to, but does not include Fiber Bragg Gratings 509B5.

A second portion of optic fiber 510B1 extends from the first portion andis configured as cantilever beam 515B. The second portion of optic fiber510B1 includes Fiber Bragg Gratings 509B5. In this aspect, optic fiber510B1 is a multi-core fiber that is equivalent to optic fiber 410B.

In this aspect, cantilever beam 515B extends from first end 51581 in aproximal direction away from the distal end of body 506B towards secondend 515B2 Second end 515B2 is the free end of cantilever beam 515B andis connected to mass 516A. Thus, in this example, free end 515B2 isproximal to fixed end 515B1. The distal and proximal directions arerepresented by arrow 595. Fiber Bragg Gratings 509B5 is positionedadjacent first end 515B1 of cantilever beam 515B. The design andfunction of accelerometer 520B is equivalent to that described abovewith respect to accelerometer 420B that was described above.

FIG. 6A is a diagram of one aspect of a portion of a surgical instrumentthat includes a force sensor and accelerometer apparatus 603, sometimesreferred to as apparatus 603. FIG. 6B is an enlarged view of the distalend of force sensor and accelerometer apparatus 603. FIG. 6C is anenlarged view of accelerometer 620Y. In FIG. 6A, components with areference numeral the same as a reference numeral in an earlier drawingare equivalent to components described with respect to the earlierdrawings, and so that description is not repeated here.

Apparatus 603 includes a force sensor and two accelerometers 620X and620Y. Apparatus 603 includes a generally annular tube 606 that in thisaspect is part of the shaft of the surgical instrument. Alternatively,as described above, apparatus 603 can be a separately manufactured unitthat can be operably coupled to a distal end of shaft 302 and that canbe operably coupled to a proximal body segment of joint 304.

The distal end of apparatus 603 is connected to a joint 304 that in turnis connected to an end component 305. Thus, apparatus 603 is proximal toand adjacent to joint 304. In particular, accelerometers 620X and 620Yof apparatus 603 are proximal to and adjacent to joint 304.

In this aspect, tube 606 does not include a number of rectangular-shapedapertures exposing a plurality of internal ribs, but tube 606 doesinclude a plurality of radial ribs 608 forming through passages forpassage of actuation cables, wires, tubes, rods, and/or flushing fluids.Plurality of radial ribs 608 are equivalent to plurality of radial ribs308 that was described above, and so instead of repeating thedescription, the description of plurality of radial ribs 308 isincorporated by reference. Of course, in another aspect, tube 606 maynot include the plurality of radial ribs.

Again, in this aspect, a number of optic fibers including optic fibers610A1, 610A2, e.g., four optic fibers, are mounted on an outer surface607 of tube 606. The four optic fibers are spaced equally, 90 degreesapart, around outer surface 607 of tube 606, but only portions of two ofthe four optic fibers are shown in FIG. 6A. The ninety-degree spacing isillustrative only and is not intended to be limiting. For examples ofother spacings between the optic fibers, see U.S. Patent ApplicationPublication No. US 2009/0157092 A1 (filed Dec. 18, 2007).

Each of optic fibers 610A1, 610A2 includes at least one strain gauge609A1, 609A2 that is used in low frequency force sensing, as describedwith respect to FIG. 3B. Optic fibers 610A1, 6510A2 may be inlaid ingrooves 611A1, 611A2 that form part of outer surface 607 of tube 606 orin a depressed area that forms part of outer surface 607 of tube 606. Inone aspect, each of the four optic fibers includes a single core.

In this aspect, accelerometers 620X and 620Y have the same physicalconfiguration, and so only accelerometer 620Y is described. Optic fiber610A1 extends onto a cantilever beam 615A with Fiber Bragg Gratingstrain gauge 609A5 positioned near a first end 615A1 of cantilever beam615A. Thus, optic fiber 610A1 carries strain information for measurementof low frequency forces and strain information for measurement ofaccelerations.

In this aspect, cantilever beam 615A extends from first end 615A1 in adistal direction away from body 606 towards second end 615A2, the freeend, which is connected to mass 616A. Thus, in this example, second end615A2 of cantilever beam 615A is distal to first end 615A1 of cantileverbeam 615A. The distal and proximal directions are represented by arrow695. The design and function of accelerometer 620X and of accelerometer620Y is equivalent to that described above with respect to accelerometer420A.

FIG. 7A is a diagram of one aspect of a portion of a surgical instrumentthat includes a force sensor and accelerometer apparatus 703, sometimesreferred to as apparatus 703. FIG. 7B is an enlarged view ofaccelerometer 720Y. In FIG. 7A, components with a reference numeral thesame as a reference numeral in an earlier drawing are equivalent tocomponents described with respect to the earlier drawings, and so thatdescription is not repeated here.

Apparatus 703 includes a force sensor and at least one accelerometer720. Apparatus 703 includes a generally annular tube 706 that, in thisaspect, is part of the shaft of the surgical instrument. Alternatively,as described above, apparatus 703 can be a separately manufactured unitthat can be operably coupled to a distal end of shaft 302 and that canbe operably coupled to a proximal body segment of joint 304.

The distal end of apparatus 703 is connected to a joint 304 that in turnis connected to an end component 305. Thus, apparatus 703 is proximal toand adjacent to joint 304. In particular, accelerometer 720 of apparatus703 is proximal to and adjacent to joint 304.

In this aspect, tube 706 does not include a number of rectangular-shapedapertures exposing a plurality of internal ribs, but tube 706 doesinclude a plurality of radial ribs forming through passages for passageof actuation cables, wires, tubes, rods, and/or flushing fluids. Theplurality of radial ribs are equivalent to plurality of radial ribs 308that was described above, and so instead of repeating the description,the description of plurality of radial ribs 308 is incorporated byreference. Of course, in another aspect, tube 706 may not include theplurality of radial ribs.

Again, in this aspect, a number of optic fibers including optic fibers710A1, 710A2, e.g., four optic fibers, are mounted on an outer surface707 of tube 706. The four optic fibers are spaced equally, 90 degreesapart, around outer surface 707 of tube 706, but only portions of two ofthe four optic fibers are shown in FIG. 7A. The ninety-degree spacing isillustrative only and is not intended to be limiting. For examples ofother spacings between the optic fibers, see U.S. Patent ApplicationPublication No. US 2009/0157092 A1 (filed Dec. 18, 2007).

Each of optic fibers 710A1, 710A2 includes at least one strain gauge709A1, 709A2 that is used in low frequency force sensing, as describedwith respect to FIG. 3B. Optic fibers 710A1, 710A2 may be inlaid ingrooves 711A1, 711A2 that form part of outer surface 707 of tube 706 orin a depressed area that forms part of outer surface 707 of tube 706.

In this aspect, force sensor and accelerometer apparatus 703 includes atleast one accelerometer 720. In this aspect, a first portion of opticfiber 710A5 is fixedly attached, e.g., epoxied, in a groove 711A5 or adepressed region in surface 707. In this example, a dedicated opticfiber 710A5 is used for accelerometer instead of one of the optic fibers710A1, 710A2 used in the force sensor.

The first portion of the optic fiber 710A5 is adjacent to, but does notinclude Fiber Bragg Grating 709A5. A second portion of optic fiber 710A5extends from the first portion and is configured as cantilever beam715A. Cantilever beam 715A is positioned in a slot 721, e.g., an openingthrough the wall of tube 706. In this aspect, optic fiber 710A5 is amulti-core fiber that is equivalent to optic fiber 410B.

In this aspect, cantilever beam 715A extends from first end 715A1 in adistal direction towards second end 715A2. Second end 715A2 is the freeend of cantilever beam 715A and is connected to mass 716A. Thus, in thisexample, second end 715A2 of cantilever beam 715A is distal to first end715A1 of cantilever beam 715A. The distal and proximal directions arerepresented by arrow 795. Fiber Bragg Grating 709A5 is positionedadjacent first end 715A1 of cantilever beam 715A. The design andfunction of accelerometer 720 is equivalent to that described above withrespect to accelerometer 420B that was described above.

Each of the accelerometers described herein is packaged in a minimumphysical volume and in an orientation consistent with the availablespace near the surgical instrument tip and consistent with the runningdirection of the other optical fiber strain sensors. In eachaccelerometer, the Fiber Bragg Grating is used singly without provisionfor temperature compensation since high pass filtering of the signaleliminates slower or direct current (DC) offset due to thermal drift.

FIG. 8 is a block diagram illustrating the processing of the informationgenerated by each of the force sensor and accelerometer apparatusesdescribed above. As described above, two different apparatuses can beused and connect to interrogator 220. A first apparatus 801A includes asurgical instrument 803A that in turn includes a force sensor 804A andan accelerometer 820A. Force sensor 804A and accelerometer 820A areequivalent to any of those described above with respect to FIGS. 4A, 5A,and 6A to 6C where the strain sensor in accelerometer 820A is in serieswith a strain sensor in force sensor 804A. A second apparatus 801B(shown by dotted lines because apparatus 801B is not connected tointerrogator 220 in this example) includes a second surgical instrument803B that in turn includes a force sensor 804B and an accelerometer820B. Force sensor 804B and accelerometer 820B are equivalent to any ofdescribed above with respect to FIGS. 4B, 5B, and 7A to 7B, where thestrain sensor in accelerometer 820B is in parallel with strain sensorsin force sensor 804B.

The reflected light from the Fiber Bragg Gratings in force sensor 804Aand the Fiber Bragg Grating in accelerometer or accelerometers 820A ofsurgical instrument 801A is changed into digital low frequency forceinformation 810 and digital accelerometer information 811.

Low frequency force information 810 is processed by a low frequencyforce feedback loop module 815, sometimes referred to as module 815. Inresponse to information 810, module 815 low pass filters information 810to generate feedback signals that are applied to a master arm 821 insurgeon's console 260. The force feedback on master arm 821 provides anindication to the surgeon of the force being applied by a surgicalinstrument. FIG. 9 is an illustration of a master tool manipulator 920that is an example of master arm 821. Master tool manipulator 920includes a base 929 and a master tool grip 921.

Accelerometer information 811 includes high frequency information aboutthe interaction between the robotic surgical instrument and the surgicalworking environment. However, accelerometer information 811 may alsoinclude low frequency information such as a DC offset due to temperaturechanges of the acceleration sensing Fiber Bragg Grating. The highfrequency information about the interaction between the robotic surgicalinstrument and the surgical working environment can be acquiredtransient strain information and/or acquired sustained time varyingstrain information.

Acceleration information 811 is first received by high pass filtermodule 831. High pass filter module 831 high pass filters theaccelerometer information. For example, high pass filter moduleattenuates signals having a frequency less than 50 Hz in one example andattenuates signals having a frequency less than 30 Hz in anotherexample. Since the thermal effect on the Fiber Bragg Grating inaccelerometer 820A is a DC offset to the output signal fromaccelerometer, high pass filter module 831 eliminates the DC offset andso eliminates any temperature effects on the signals output fromaccelerometer 820A. In addition, the high pass filtering minimizesinteraction with low frequency force feedback loop 815 that outputsfeedback information from an accompanying low frequency force transduceron surgical robot master arm 821. The output from high pass filtermodule 831 is input to a power limiter module 832 in vibro-tactilefeedback module 231.

Power limiter module 832 is configured to limit the power sent to thevibro-tactile output device 822 on master arm hand piece, i.e., limitmaster arm hand piece feedback. The goal of the power limiter is tolimit the size of the control signal sent to the audio output 840, thevibro-tactile device 822, and/or the master arm 821 such that eachdevice is not being asked to actuate outside of its intended range. Theintended range may be specified by limits on the hardware or may be setby the desired application.

Power limiter module 832 can be implemented in a number of ways. Forexample, power limiter module 831 can limit the amplitude of signalspassed through module 831. Alternatively, power limiter module 832 canbe configured as a low pass filter that attenuates signals havingfrequencies above a maximum frequency of interest for vibro-tactilefeedback, e.g., above 200 Hz. In another aspect, power limiter module832 is configured as a fixed frequency cut-off filter so that signalshaving frequencies above a maximum frequency of interest forvibro-tactile feedback are effectively blocked from passing throughpower limiter module 832. Alternatively, any combination of theseimplementations of power limiter module 832 could be used to limitpassing signals above the frequency range of surgical interest and toprevent any detrimental feedback effect involving accelerometer 820A andthe vibro-tactile device. Additionally, if multiple accelerometers existon the force sensor and accelerometer apparatus 303, the power limitermay combine multiple accelerometer signals into a single signal.

The output from the power limiter module 832 drives a real time directvibro-tactile haptic output device 822 attached to the surgical robotmaster hand piece, gimbal, or finger grip levers 2. In FIG. 9,vibro-tactile haptic output device 931 is mounted on master tool grip921. A hardware amplifier may exist between the high pass filter 832 andthe vibro-tactile device 822 or the vibro-tactile device may have aself-contained amplifier.

Vibro-tactile output device 931, for example, includes a voice coilmotor and movable counter mass attached to the master tool grip 921where the forces induced by acceleration of the counter mass are felt onthe surgeon's fingertips. This permits output of higher frequencycontent of the forces exerted on the robotic surgical instrument tipthan may be output by attempting to move entire master manipulatorassembly 920 itself. Movement of entire master manipulator assembly 920is more suited to output of the lower frequency content of sensedinstrument tip forces from low frequency force feedback loop 815.

Optionally, the output from the power limiter module 832 is sent to themaster arm. The master arm adds the output from the high pass filter 832to the output of the low frequency force feedback loop 815. The masterarm outputs both the low frequency force signal and the high frequencyacceleration signals to the surgeon. The high pass filter output 832 maybe sent to only one motor of the master arm, e.g. the distal roll axison the master tool grip 921, which is better suited to output the highfrequency content rather than outputting the high frequency content viathe entire master arm.

Optionally, the output from high pass filter 832 is input to an audiooutput circuit 840 that in turn drives speaker 841. Speaker 841co-displays the acquired time varying strain information as an acousticsignal audible to the surgeon and/or other operating room staff in realtime.

While above the operation of the elements in FIG. 8 was described withrespect to apparatus 801A with surgical instrument 803A, the descriptionis also directly applicable when apparatus 801B with surgical instrument803B is used. Thus, the description of FIG. 8 is not repeated withapparatus 801B connected to interrogator 220 in place of apparatus 801A.

The above description and the accompanying drawings that illustrateaspects and embodiments of the present inventions should not be taken aslimiting—the claims define the protected inventions. Various mechanical,compositional, structural, electrical, and operational changes may bemade without departing from the spirit and scope of this description andthe claims. In some instances, well-known circuits, structures, andtechniques have not been shown or described in detail to avoid obscuringthe invention.

Further, this description's terminology is not intended to limit theinvention. For example, spatially relative terms-such as “beneath”,“below”, “lower”, “above”, “upper”, “proximal”, “distal”, and thelike—may be used to describe one element's or feature's relationship toanother element or feature as illustrated in the figures. Thesespatially relative terms are intended to encompass different positionsand orientations of the device in use or operation in addition to theposition and orientation shown in the figures. For example, if thedevice in the figures is turned over, elements described as “below” or“beneath” other elements or features would then be “above” or “over” theother elements or features. Thus, the exemplary term “below” canencompass both positions and orientations of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly.

The singular forms “a”, “an”, and “the” are intended to include theplural forms as well, unless the context indicates otherwise. The terms“comprises”, “comprising”, “includes”, and the like specify the presenceof stated features, steps, operations, elements, and/or components butdo not preclude the presence or addition of one or more other features,steps, operations, elements, components, and/or groups.

All examples and illustrative references are non-limiting and should notbe used to limit the claims to specific implementations and embodimentsdescribed herein and their equivalents. Any headings are solely forformatting and should not be used to limit the subject matter in anyway, because text under one heading may cross-reference or apply to textunder one or more headings. Finally, in view of this disclosure,particular features described in relation to one aspect or embodimentmay be applied to other disclosed aspects or embodiments of theinvention, even though not specifically shown in the drawings ordescribed in the text.

Embodiments described above illustrate but do not limit the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the present invention.Accordingly, the scope of the invention is defined only by the followingclaims.

We claim:
 1. A medical device comprising: a shaft; an end componentcoupled to the shaft by a joint; and an accelerometer coupled to theshaft proximal to the joint, the accelerometer comprising a cantileverbeam and a strain sensor, the cantilever beam being formed in a wall ofa tube body coupled to the end component, the cantilever beam being aportion of the wall positioned in a slot through-opening in the tubebody, the strain sensor being affixed to the cantilever beam.
 2. Themedical device of claim 1, the accelerometer being included in a distalportion of the shaft.
 3. The medical device of claim 1, furthercomprising a force transducer comprising the tube body, the forcetransducer including the accelerometer, and the force transducer beingmounted between a distal end of the shaft and the joint.
 4. The medicaldevice of claim 1, the strain sensor being mounted on the cantileverbeam a distance from a neutral axis of bending of a combination of thecantilever beam and the strain sensor.
 5. The medical device of claim 1,further comprising a mass positioned at a free end of the cantileverbeam.
 6. The medical device of claim 1, further comprising a mass formedintegrally with the cantilever beam, the mass being at a free end of thecantilever beam.
 7. The medical device of claim 1, further comprising atravel stop configured to limit deflection of the cantilever beam. 8.The medical device of claim 1, further comprising: a master controldevice configured to control a location of the end component; and avibro-tactile haptic output device coupled to the accelerometer and tothe master control device, wherein the vibro-tactile haptic outputdevice is configured to output haptic communication of accelerometerinformation.
 9. The medical device of claim 8, further comprising afilter coupled to the accelerometer and to the vibro-tactile hapticoutput device, wherein the filter receives accelerometer informationfrom the accelerometer, and wherein the filter outputs to thevibro-tactile haptic output device a subset of the accelerometerinformation received from the accelerometer, said subset ofaccelerometer information comprising accelerometer information that iswithin a pre-determined frequency range.
 10. The medical device of claim1, further comprising a sound system coupled to the accelerometer, thesound system being configured to generate an audible acoustic signal inresponse to accelerometer information.
 11. The medical device of claim1, further comprising a master control device configured to control alocation of the end component, the master control device beingconfigured to generate a haptic signal in response to accelerometerinformation.